<template>
    <table
        cellspacing="0"
        cellpadding="0"
        class="zx-date-table"
        :class="{ 'is-week-mode': selectionMode === 'week' }"
        @click="handleClick"
        @mousemove="handleMouseMove"
    >
        <tbody>
            <tr>
                <th v-if="showWeekNumber">{{ t('el.datepicker.week') }}</th>
                <th v-for="(week, key) in WEEKS" :key="key">{{ t('el.datepicker.weeks.' + week) }}</th>
            </tr>
            <tr
                v-for="(row, key) in rows"
                :key="key"
                class="zx-date-table__row"
                :class="{ current: isWeekActive(row[1]) }"
            >
                <td
                    v-for="(cell, key) in row"
                    :key="key"
                    :class="getCellClasses(cell)"
                >
                    <div>
                        <span>
                            {{ cell.text }}
                        </span>
                    </div>
                </td>
            </tr>
        </tbody>
    </table>
</template>

<script>
import { getFirstDayOfMonth, getDayCountOfMonth, getWeekNumber, getStartDateOfMonth, prevDate, nextDate, isDate, clearTime as _clearTime } from '@src/utils/date-util';
import Locale from '@src/mixins/locale';
import { arrayFindIndex, arrayFind, coerceTruthyValueToArray } from '@src/utils/util';

const WEEKS = ['sun', 'mon', 'tue', 'wed', 'thu', 'fri', 'sat'];
const getDateTimestamp = function (time) {
    if (typeof time === 'number' || typeof time === 'string') {
        return _clearTime(new Date(time)).getTime();
    } else if (time instanceof Date) {
        return _clearTime(time).getTime();
    } else {
        return NaN;
    }
};

// remove the first element that satisfies `pred` from arr
// return a new array if modification occurs
// return the original array otherwise
const removeFromArray = function (arr, pred) {
    const idx = typeof pred === 'function' ? arrayFindIndex(arr, pred) : arr.indexOf(pred);
    return idx >= 0 ? [...arr.slice(0, idx), ...arr.slice(idx + 1)] : arr;
};

export default {
    mixins: [Locale],

    props: {
        firstDayOfWeek: {
            default: 7,
            type: Number,
            validator: val => val >= 1 && val <= 7,
        },

        value: {},

        defaultValue: {
            validator(val) {
                // either: null, valid Date object, Array of valid Date objects
                return val === null || isDate(val) || (Array.isArray(val) && val.every(isDate));
            },
        },

        date: {},

        selectionMode: {
            default: 'day',
        },

        showWeekNumber: {
            type: Boolean,
            default: false,
        },

        disabledDate: {},

        cellClassName: {},

        minDate: {},

        maxDate: {},

        rangeState: {
            default() {
                return {
                    endDate: null,
                    selecting: false,
                };
            },
        },
    },

    data() {
        return {
            tableRows: [[], [], [], [], [], []],
            lastRow: null,
            lastColumn: null,
        };
    },

    computed: {
        offsetDay() {
            const week = this.firstDayOfWeek;
            // 周日为界限，左右偏移的天数，3217654 例如周一就是 -1，目的是调整前两行日期的位置
            return week > 3 ? 7 - week : -week;
        },

        WEEKS() {
            const week = this.firstDayOfWeek;
            return WEEKS.concat(WEEKS).slice(week, week + 7);
        },

        year() {
            return this.date.getFullYear();
        },

        month() {
            return this.date.getMonth();
        },

        startDate() {
            return getStartDateOfMonth(this.year, this.month);
        },

        rows() {
            // TODO: refactory rows / getCellClasses
            const date = new Date(this.year, this.month, 1);
            let day = getFirstDayOfMonth(date); // day of first day
            const dateCountOfMonth = getDayCountOfMonth(date.getFullYear(), date.getMonth());
            const dateCountOfLastMonth = getDayCountOfMonth(date.getFullYear(), (date.getMonth() === 0 ? 11 : date.getMonth() - 1));

            day = (day === 0 ? 7 : day);

            const offset = this.offsetDay;
            const rows = this.tableRows;
            let count = 1;

            const startDate = this.startDate;
            const disabledDate = this.disabledDate;
            const cellClassName = this.cellClassName;
            const selectedDate = this.selectionMode === 'dates' ? coerceTruthyValueToArray(this.value) : [];
            const now = getDateTimestamp(new Date());

            for (let i = 0; i < 6; i++) {
                const row = rows[i];

                if (this.showWeekNumber) {
                    if (!row[0]) {
                        row[0] = { type: 'week', text: getWeekNumber(nextDate(startDate, i * 7 + 1)) };
                    }
                }

                for (let j = 0; j < 7; j++) {
                    let cell = row[this.showWeekNumber ? j + 1 : j];
                    if (!cell) {
                        cell = { row: i, column: j, type: 'normal', inRange: false, start: false, end: false };
                    }

                    cell.type = 'normal';

                    const index = i * 7 + j;
                    const time = nextDate(startDate, index - offset).getTime();
                    cell.inRange = time >= getDateTimestamp(this.minDate) && time <= getDateTimestamp(this.maxDate);
                    cell.start = this.minDate && time === getDateTimestamp(this.minDate);
                    cell.end = this.maxDate && time === getDateTimestamp(this.maxDate);
                    const isToday = time === now;

                    if (isToday) {
                        cell.type = 'today';
                    }

                    if (i >= 0 && i <= 1) {
                        const numberOfDaysFromPreviousMonth = day + offset < 0 ? 7 + day + offset : day + offset;

                        if (j + i * 7 >= numberOfDaysFromPreviousMonth) {
                            cell.text = count++;
                        } else {
                            cell.text = dateCountOfLastMonth - (numberOfDaysFromPreviousMonth - j % 7) + 1 + i * 7;
                            cell.type = 'prev-month';
                        }
                    } else {
                        if (count <= dateCountOfMonth) {
                            cell.text = count++;
                        } else {
                            cell.text = count++ - dateCountOfMonth;
                            cell.type = 'next-month';
                        }
                    }

                    const cellDate = new Date(time);
                    cell.disabled = typeof disabledDate === 'function' && disabledDate(cellDate);
                    cell.selected = arrayFind(selectedDate, date => date.getTime() === cellDate.getTime());
                    cell.customClass = typeof cellClassName === 'function' && cellClassName(cellDate);
                    this.$set(row, this.showWeekNumber ? j + 1 : j, cell);
                }

                if (this.selectionMode === 'week') {
                    const start = this.showWeekNumber ? 1 : 0;
                    const end = this.showWeekNumber ? 7 : 6;
                    const isWeekActive = this.isWeekActive(row[start + 1]);

                    row[start].inRange = isWeekActive;
                    row[start].start = isWeekActive;
                    row[end].inRange = isWeekActive;
                    row[end].end = isWeekActive;
                }
            }

            return rows;
        },
    },

    watch: {
        'rangeState.endDate'(newVal) {
            this.markRange(this.minDate, newVal);
        },

        minDate(newVal, oldVal) {
            if (getDateTimestamp(newVal) !== getDateTimestamp(oldVal)) {
                this.markRange(this.minDate, this.maxDate);
            }
        },

        maxDate(newVal, oldVal) {
            if (getDateTimestamp(newVal) !== getDateTimestamp(oldVal)) {
                this.markRange(this.minDate, this.maxDate);
            }
        },
    },

    methods: {
        cellMatchesDate(cell, date) {
            const value = new Date(date);
            return this.year === value.getFullYear() &&
                this.month === value.getMonth() &&
                Number(cell.text) === value.getDate();
        },

        getCellClasses(cell) {
            const selectionMode = this.selectionMode;
            const defaultValue = this.defaultValue ? Array.isArray(this.defaultValue) ? this.defaultValue : [this.defaultValue] : [];

            const classes = [];
            if ((cell.type === 'normal' || cell.type === 'today') && !cell.disabled) {
                classes.push('available');
                if (cell.type === 'today') {
                    classes.push('today');
                }
            } else {
                classes.push(cell.type);
            }

            if (cell.type === 'normal' && defaultValue.some(date => this.cellMatchesDate(cell, date))) {
                classes.push('default');
            }

            if (selectionMode === 'day' && (cell.type === 'normal' || cell.type === 'today') && this.cellMatchesDate(cell, this.value)) {
                classes.push('current');
            }

            if (cell.inRange && ((cell.type === 'normal' || cell.type === 'today') || this.selectionMode === 'week')) {
                classes.push('in-range');

                if (cell.start) {
                    classes.push('start-date');
                }

                if (cell.end) {
                    classes.push('end-date');
                }
            }

            if (cell.disabled) {
                classes.push('disabled');
            }

            if (cell.selected) {
                classes.push('selected');
            }

            if (cell.customClass) {
                classes.push(cell.customClass);
            }

            return classes.join(' ');
        },

        getDateOfCell(row, column) {
            const offsetFromStart = row * 7 + (column - (this.showWeekNumber ? 1 : 0)) - this.offsetDay;
            return nextDate(this.startDate, offsetFromStart);
        },

        isWeekActive(cell) {
            if (this.selectionMode !== 'week') return false;
            const newDate = new Date(this.year, this.month, 1);
            const year = newDate.getFullYear();
            const month = newDate.getMonth();

            if (cell.type === 'prev-month') {
                newDate.setMonth(month === 0 ? 11 : month - 1);
                newDate.setFullYear(month === 0 ? year - 1 : year);
            }

            if (cell.type === 'next-month') {
                newDate.setMonth(month === 11 ? 0 : month + 1);
                newDate.setFullYear(month === 11 ? year + 1 : year);
            }

            newDate.setDate(parseInt(cell.text, 10));

            if (isDate(this.value)) {
                const dayOffset = (this.value.getDay() - this.firstDayOfWeek + 7) % 7 - 1;
                const weekDate = prevDate(this.value, dayOffset);
                return weekDate.getTime() === newDate.getTime();
            }
            return false;
        },

        markRange(minDate, maxDate) {
            minDate = getDateTimestamp(minDate);
            maxDate = getDateTimestamp(maxDate) || minDate;
            [minDate, maxDate] = [Math.min(minDate, maxDate), Math.max(minDate, maxDate)];

            const startDate = this.startDate;
            const rows = this.rows;
            for (let i = 0, k = rows.length; i < k; i++) {
                const row = rows[i];
                for (let j = 0, l = row.length; j < l; j++) {
                    if (this.showWeekNumber && j === 0) continue;

                    const cell = row[j];
                    const index = i * 7 + j + (this.showWeekNumber ? -1 : 0);
                    const time = nextDate(startDate, index - this.offsetDay).getTime();

                    cell.inRange = minDate && time >= minDate && time <= maxDate;
                    cell.start = minDate && time === minDate;
                    cell.end = maxDate && time === maxDate;
                }
            }
        },

        handleMouseMove(event) {
            if (!this.rangeState.selecting) return;

            let target = event.target;
            if (target.tagName === 'SPAN') {
                target = target.parentNode.parentNode;
            }
            if (target.tagName === 'DIV') {
                target = target.parentNode;
            }
            if (target.tagName !== 'TD') return;

            const row = target.parentNode.rowIndex - 1;
            const column = target.cellIndex;

            // can not select disabled date
            if (this.rows[row][column].disabled) return;

            // only update rangeState when mouse moves to a new cell
            // this avoids frequent Date object creation and improves performance
            if (row !== this.lastRow || column !== this.lastColumn) {
                this.lastRow = row;
                this.lastColumn = column;
                this.$emit('changerange', {
                    minDate: this.minDate,
                    maxDate: this.maxDate,
                    rangeState: {
                        selecting: true,
                        endDate: this.getDateOfCell(row, column),
                    },
                });
            }
        },

        handleClick(event) {
            let target = event.target;
            if (target.tagName === 'SPAN') {
                target = target.parentNode.parentNode;
            }
            if (target.tagName === 'DIV') {
                target = target.parentNode;
            }

            if (target.tagName !== 'TD') return;

            const row = target.parentNode.rowIndex - 1;
            const column = this.selectionMode === 'week' ? 1 : target.cellIndex;
            const cell = this.rows[row][column];

            if (cell.disabled || cell.type === 'week') return;

            const newDate = this.getDateOfCell(row, column);

            if (this.selectionMode === 'range') {
                if (!this.rangeState.selecting) {
                    this.$emit('pick', { minDate: newDate, maxDate: null });
                    this.rangeState.selecting = true;
                } else {
                    if (newDate >= this.minDate) {
                        this.$emit('pick', { minDate: this.minDate, maxDate: newDate });
                    } else {
                        this.$emit('pick', { minDate: newDate, maxDate: this.minDate });
                    }
                    this.rangeState.selecting = false;
                }
            } else if (this.selectionMode === 'day') {
                this.$emit('pick', newDate);
            } else if (this.selectionMode === 'week') {
                const weekNumber = getWeekNumber(newDate);
                const value = newDate.getFullYear() + 'w' + weekNumber;
                this.$emit('pick', {
                    year: newDate.getFullYear(),
                    week: weekNumber,
                    value: value,
                    date: newDate,
                });
            } else if (this.selectionMode === 'dates') {
                const value = this.value || [];
                const newValue = cell.selected
                    ? removeFromArray(value, date => date.getTime() === newDate.getTime())
                    : [...value, newDate];
                this.$emit('pick', newValue);
            }
        },
    },
};
</script>
